In recent years, concern over the quality of drinking water in the United States and elsewhere has stimulated the need for development of drinking water purification in the home and workplace.
The popularity of recreational vehicles and other outdoor recreational activities in areas where municipal water treatment facilities are not available has inspired a demand for portable water purification devices. In many places, homes do not have a purified water source and must rely upon wells or other natural sources which require treatment to provide safe, clean, palatable water. Chlorine added to water to render it bacteriologically safe produces distasteful odor and an undesirable taste.
Filtration systems for home use have been devised which utilize cartridges. The cartridges are elongated cylinders closed at one end by a domed shaped formation. The cartridges are contained in a vessel with an inlet which communicate with the vessel externally of the cartridge and the outlet communicates with the open end of the cartridge. The cartridges are of various porous materials.
The inlet and outlet are connected in series with the water line and the water pressure drives the water through the porous material to the outlet. These must be installed into the source water line and require in line pressure.
A proper in line filter can remove harmful and distasteful contaminants but requires a plumbing installation and is not useful in field or traveling situations. Ceramic cartridge filters are expensive and difficult to clean and maintain.
The gravity filter of the present invention provides a water treatment system which can be utilized in situations where present filtration devices are inconvenient or impractical; it satisfies certain needs not covered by known systems and provides an economical alternative.
The intersticial spaces between in particles of which an integrally molded filter element of high density ceramic incorporating carbon and silver salts averages about two microns. It takes about four to five hours for two quarts of water to pass through such an element.
Increased flow may be achieved by stacking a ceramic filter element incorporating silver salts and a carbon filter element impregnated with calcium carbonate together to form a filter unit. The stacked elements reduce the time to pass two quarts of water through the filter unit to approximately twenty to thirty minutes. This is accomplished by eliminating the carbon in the ceramic element. The interstices in the ceramic element are increased in size to between five and eight microns. The flow rate through the calcium carbonate impregnated carbon element is approximately the same as through the ceramic element of this embodiment. Thus the flow rate is multiplied by ten relative to the single layer filter element.
If the effectiveness of each layer is reduced to ninety percent in order to increase the flow rate, then stacked together, ninety nine percent removal would be achieved. It should be noted that the silver in effect sterilizes the bacteria. The carbon eliminates the chlorine taste. The calcium carbonate eliminates distasteful minerals and replaces a portion of the removed minerals with the more desirable tasting calcium. It has been determined that a ph rating of 7.2 produces the most palatable taste in water for drinking coffee etc. The calcium carbonate maintains the ph at 7.2.
It has not been possible to incorporate ion exchange resins into integrally molded filters because they would be burned out during the molding process. Ion exchange resins are known to remove inorganic salts as well as heavy metals and their oxides and other undesirable impurities. They are known to coagulate particles in the water supply to make them more suitable for filtration and to convert soluble contaminants to insoluble precipitates. Beads of ion exchange resins can be sandwiched between the stacked filter elements. Manganese dioxide may be used to perform the function of the ion exchange resins and can be incorporated in the carbon element.